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What effect does the change in temperature have on the reaction rate of the reaction between sodium thiosulphate and hydrochloric acid?

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Introduction

QASMT Chemistry IA Rate of Reaction Dr Natt Jeremiah Joseph 12/10/09 Research Question: What effect does the change in temperature have on the reaction rate of the reaction? Aim: To investigate the effect of temperature on reaction rate and to determine how k, the rate constant, varies with the temperature and to determine the activation energy for the rate determining step of the reaction. Background Information: The reaction between sodium thiosulphate and hydrochloric acid can be represented by the equation S2O32-(aq) + 2H+ (aq) ==> S(s) + SO2 (aq) + H2O (l) The time taken for the precipitate of sulphur to obscure a cross marked on a piece of the paper placed the reaction flask is used as a measure of the reaction rate. The less time taken for the cross to 'disappear', the faster is the rate of reaction. Data Collection and Processing: Thermometer Error: � 0.05�C Stopwatch Error: � 0.5 seconds Measuring Cylinder Error: � 0.5 ml Time(secs) � 0.5 Initial Temperature(K) �0.05 Final Temperature(K) �0.05 Average Temperature(K) � 0.1 557 303 297 300 273 313 309 311 227 323 319 321 116 333 330 331.5 93.0 343 341 342 The errors were too insignificant to be included in any of the graphs. ...read more.

Middle

This equation is derived from the above equation and is shown below. The y intercept on this graph will provide and the gradient of the graph will provide. The Graph of ln (k) over 1/T is shown below. The equation for the graph above is in the form of y=mx + c. Where m is the gradient and c is the y intercept. Therefore, m = - (Ea/R) = -4421 and c = ln (A) = 8.37. Activation Energy: -4421 = - (Ea/R) where R = 8.314 - 4421 � 8.314 = -Ea ? Ea = 36760 J = 36.76 KJ mol-1 Conclusion and Evaluation: The activation energy calculated was 36.76 KJ mol-1. However, the theoretical activation energy for this reaction is defined as 52 KJ mol-1. This shows that there were problems with the experiment. Although the reaction rate discovered from the experiment differs from the theoretical reaction rate the reaction rate found from the experiment supports the experiment. This is because when the variables are plot into the equation the answer supports the data recorded. ...read more.

Conclusion

This makes the reaction time error of the reading of the time constant, as the same person with the same reaction time is used throughout the experiment. Additionally, more repeats of the experiment need to be made. This reduces the effect of an outlier as the readings are all averaged. The aim was successfully achieved because the relationship between temperature and reaction rate was successfully investigated. The relationship is shown through all the graphs and tables shown above. The first graph shows that there is an exponential relationship between the rate of reaction and the temperature. This means that as temperature increases the rate of reaction increases by a factor of approximately 2. It also shows that the reaction is second order. The second graph provides the negative gradient needed for the calculations and the third graph gives the data to find the activation energy. The R2 value showed on the third graph shows how accurate the line of best fit. An R2 value of 1 shows that the line of best fit perfectly matches the data points. Therefore, an R2 value of 0.9629 shows that the data points were accurate. ...read more.

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